During a frost quake the ground shakes and a loud boom sound can be heard.

News 8 meteorologist Matt Moore says frost quakes occur when ground water travels below the surface and freezes. When the water melts there is a void and the ground can come together - similar to an earthquake.

The incident occurred at a construction site behind Franklin and Marshall College's "College Row Apartments." Crews were working to dismantle an old, metal bridge. A spokesperson for F&M says they were told the sound was cryoseismic activity or a frost quake.

One construction worker was hit in the back with some rocks and a window lying on a backhoe became cracked.

All equipment at the site was checked and is working properly. Only an air compressor was in use at the time of the incident.

Witnesses described it as a loud explosion. A mounted police officer also reported the explosion while patrolling the area around Clipper Magazine Stadium.